Telecommunications power systems generally employ rectifiers that generate a direct current (DC) voltage from an alternating current (AC) power source. Distribution modules include circuit breakers that connect the rectifiers to loads and that distribute current to the loads. The loads in a telecommunications power system typically include telephone switches, cellular equipment, routers and other associated equipment. In the event that AC power is lost, the telecommunications power systems initially rely on backup batteries to provide power and to prevent costly down time. Generators are typically used for longer outages. Telephone switches, cellular equipment and routers normally carry thousands of calls and/or data streams that will be interrupted if power is lost causing a significant loss of revenue.
The backup batteries provide power for a predetermined backup period. The number and size of the backup batteries that are required to provide power during the predetermined backup period varies depending on the number and size of the loads. The backup batteries should provide a sufficient time to allow skilled technicians to reach the site, to troubleshoot and to fix the problem or to connect a backup generator. Some systems use backup batteries until a generator that provides backup AC power is started to temporarily provide power when the AC power source is lost. While AC power is out, the generator provides power for the loads and charges the back up batteries. As a margin of safety, the capacity of the generator is generally 20% larger than the maximum power required to supply the loads and to charge the backup batteries. As can be appreciated, the cost of the generator increases significantly as capacity increases.
In an effort to limit the size of the backup generator to reduce the cost of the telecommunications power system, some operators separate the DC power bus into first and second sections. A contactor provides a connection between the first and second sections of the DC power bus and is normally closed. When AC power is lost, the contactor is opened. A generator that is connected to the first section provides power to the loads but does not charge the backup batteries. When the AC power source returns, the generator shuts down or is placed in a standby mode. The contactor is closed and the system returns to normal operation.
Other systems that employ the split DC power bus with the first and second sections do not use the contactor between the first and second sections. In these systems, the rectifiers that charge the backup batteries are not available for load sharing and temperature stress distribution during normal operation.
A telecommunications power system according to the invention includes a power bus and a plurality of batteries that are connected to the power bus. A distribution module is connected to the power bus. A plurality of loads are connected to the distribution module. A plurality of rectifier modules are connected to the power bus and at least one AC power source. A generator provides backup AC power to the rectifier modules when the AC power source is interrupted. A controller is connected to the rectifier modules and the generator. The controller includes a battery recharge control module that allows the user to select a first mode of operation that allows the generator to recharge the backup batteries when the generator provides the backup AC power. A second mode of operation prevents the batteries from recharging when the generator provides the backup AC power. A third mode of operation decreases current provided by the generator to charge the batteries when the generator is in an overload state until the generator is not in the overload state. A fourth mode of operation prevents the batteries from recharging when the generator is in an overload state.
The backup battery recharge controller according to the invention allows the telecommunications power system operator to prevent the backup batteries from charging when the generator provides backup AC power. As a result, a smaller generator can be used to provide the backup AC power to the loads when the AC power source is interrupted. Alternately, the telecommunications power system operator can limit the amount of current supplied to the backup batteries when the generator is in an overload state. This mode of operation allows the backup batteries to charge when excess capacity is available from the generator.